There is provided a process for producing a resin composition in a safe and cost-effective manner, the resin composition being a dispersion of active particles reactive with oxygen in a thermoplastic resin. The process is one for producing a resin composition containing at least a thermoplastic resin and active particles that have been dispersed in the thermoplastic resin and are reactive with oxygen in an atmosphere, the process comprising the steps of: protecting the active particles with a dispersion medium to prevent oxygen in the atmosphere from contacting with the active particles; removing the dispersion medium while melt-kneading the thermoplastic resin and the active particles protected with the dispersion medium to replace the dispersion medium with the thermoplastic resin; and cooling and solidifying the thermoplastic resin with the active particles dispersed therein.